Interfacial layer-free ZrO2 on Ge with 0.39-nm EOT, κ∼43, ∼2×10−3 A/cm2 gate leakage, SS =85 mV/dec, Ion/Ioff =6×105, and high strain response

Abstract

0.39-nm ultrathin EOT ZrO₂ having κ value as high as ~43 without an interfacial layer (IL) is demonstrated on Ge substrates. The EOT and gate leakage are much lower than the recent reported data [1]. In situ NH₃/H₂ remote plasma treatment (RPT) after RTO-grown ultrathin (<;1nm) GeO₂/Ge and prior to PEALD ZrO₂ leads to the formation of tetragonal phase ZrO₂ and the inhibition of GeO_x IL regrowth. As the number of RPT cycles increases, it is observed that not only higher [N] but more GeO₂ component formed on Ge surface. GeO diffuses into ZrO₂ layer via the interface reaction (Ge+GeO₂ → 2GeO) and stabilize the tetragonal phase ZrO₂. The gate dielectric has a leakage current ~10⁴X lower than other reported dielectrics in this EOT region. Ge (001) pMOSFET has low SS of 85 mV/dec and high I_on/I_off of ~6×10⁵ at V_d= -1V, while nMOSFET has SS of 90 mV/dec and I_on/I_off of ~1×10⁵ at V_d=1V. The peak electron mobility is determined by the remote phonon scattering stemming from the high-κ value. The biaxial tensile strain of ~0.04% applied on Ge (111) nMOSFET with an EOT=0.78nm produces a 4.8% drain current enhancement along the <;110> channel.